Refrigeration units used in commercial establishments for the display and storage of food products commonly have insulated glass door assemblies which permit viewing of the products in the refrigeration cabinet by passing customers. Customers typically open and close the doors frequently to obtain access to the frozen products. Each time the door is opened, relatively warm ambient air is permitted to enter the refrigeration cabinet. When the door is again closed, this relatively warm air is cooled and contracts and tends to create a vacuum within the cabinet. The vacuum which is thus created sucks or draws in further ambient air through points of least resistance throughout the cabinet. As such ambient air is being drawn into the freezer cabinet, it often is cooled below the dew point of temperature of the air, causing condensation of moisture and the undesirable build up of moisture and frost at or near the point of entry. Such build up creates an unsightly appearance and, in severe cases, can impede operation of the doors.
To overcome this problem, it has been the practice heretofore to form apertures in the sealing gasket about the perimeter of the door in order to create passageways through which ambient air may be drawn as a result of suction developed within the refrigeration cabinet. Since the gasket is relatively flexible, it has been necessary to include rigid spacer elements within the gasket to prevent the venting apertures from being closed when the gasket is pressed into sealing engagement with the refrigerator cabinet. During use of such an arrangement, it has been found that condensation from ambient air that is cooled during passage through such venting apertures tends to accumulate and sometimes freeze within the gasket, impeding its effective sealing ability. Moreover, such arrangements have not enabled existing refrigeration cabinets to be easily converted in the field to have venting capability. Proposals to provide venting apertures in the cabinet itself have not met with favor since they require significant modifications to the refrigerator cabinet and the multi-layered insulation therein.